Well, I'd assume that the division that makes batteries is separate from the other major parts of the company (like the record label and the Playstation). Most large companies are broken up into smaller companies to protect from just this sort of thing. Fortunately for Sony, their batteries have yet to seriously injure anyone (at least that I've heard). Imagine if one of their batteries caused an office to catch on fire or a plane to crash! At this point, the best they can hope for is avoiding class action lawsuits.